The present invention relates to programmer timers for appliances such as dishwashers, clothes washers, and clothes driers. Appliances of this type commonly utilize a synchronous timing motor to drive a cam mechanism for actuating a plurality of cam follower actuated switches for making and breaking individual electrical circuits for various control functions of the appliance. Programmer-timers of this type operate to control the appliance function in timed sequence and duration for providing a preselected program cycle of appliance operation.
It is known to provide appliance programmer timers having a plurality of rotary cams mounted for rotation about a common axis with the cam being rotationally advanced by a stepping mechanism. In programmer/timers of this known type, ratchet wheels are provided for advancing the rotary cams and a motor driven oscillating pawl engages the ratchet wheel for step-by-step advancement of the cam. The advance pawl may be driven by a rotating eccentric or crankshaft attached to a suitable gear reduction mechanism driven by the synchronous timing motor.
Known programmer/timers employing a synchronous timing motor have employed a ratchet mechanism in the synchronous motor to prevent reverse rotation startup of the motor which is an inherent feature of a synchronous motor. This antireverse feature in the motor has been necessitated in order to prevent reverse rotation of the drive mechanism for the ratchet advance pawl. Where the ratchet advance pawl is driven by a rotating crank or eccentric, reverse rotation of the eccentric has caused the drive pawl to "kick out" or disengage from the ratchet teeth and thereby malfunction in advancing the cam.
In programmer/timers for appliances, it is known to provide axially adjacent ratchet wheels having different pitch diameters for the peripheral teeth thereof but utilize the same pitch for the teeth of both wheels in order that a single drive pawl may actuate both ratchet wheels. It is also known to provide an intermittent series of deeper notches on one ratchet wheel to permit the drive pawl to periodically advance the first and second ratchet wheels together for a single step. This arrangement provides for faster advancement of the cam attached to the ratchet having the greater tooth pitch diameter than the cam attached to the second ratchet wheel.
Moreover, it has been desired to provide a programmer timer having a convenient low cost means for providing actuation of a separate cam follower at sub-intervals of advancement of the main ratchet wheel. Sub-interval cam follower actuation may then be employed to modify the actuation of a set of contacts actuated by either the fast or slow cam wheel or to actuate a separate set of electrical contacts.
Appliance programmer/timers have heretofor employed a separate timing motor attached to a housing which contained the escapement, cams, cam followers and electrical contacts. The gear reduction mechanism for driving the escapement has heretofore usually been incorporated in the separate motor housing. This arrangement permits separate assembly of the motor and timer mechanism; however, such an arrangement has the disadvantage of increased cost associated with separate housings for the motor and the timer mechanism.
Thus, it has been desired to provide an appliance programmer timer having a synchronous motor driven cam advance mechanism which eliminates the need for an anti-reverse directional ratchet mechanism on the timing motor and accommodates rotation of the timing motor in either direction without malfunction of the escapement. It has further been desired to provide a low cost programmer timer with the motor and timer assembled as a unit in an integral housing thereby eliminating the need for separate motor and timer housings. It has further been desired to provide a simple and low cost programmer timer having a sub-interval timed electrical switching function with relation to the timing interval employed by the main switching sequence.